The present invention relates to a refrigeration system including multiple compressors, and more particularly to mechanical subcooling of the refrigeration system to maximize operating efficiency.
In refrigeration systems, such as those used in cooling display cases of refrigeration merchandisers, it is necessary to maintain a constant temperature in the display cases to ensure the quality and condition of the stored commodity. Many factors demand varying the cooling loads on evaporators cooling the display cases. Therefore, selective operation of the compressor of the refrigeration system at different cooling capacities corresponds to the cooling demand of the evaporators. In refrigeration systems utilizing existing scroll and screw compressors, an economizer cycle is used to increase the refrigeration capacity and improve efficiency of the refrigeration system. In the economizer cycle of existing scroll and screw compressors, gas pockets in the compressor create a second “piston” as mechanical elements of the compressor proceed through the compression process.
Existing refrigeration systems with parallel compressors and mechanical subcooling do not operate most efficiently. Typically, such systems do not permit the intermediate pressure (i.e., the evaporating pressure of the subcooling compressor or compressors) and/or temperature to be adjusted to maximize efficiency of the refrigeration system.